form {
    width: 343px;
    height: 200px;
    margin: 0 auto;
    border: 1px solid rgba(0, 0, 0, 1);
    border-radius: 5px;
    overflow: hidden;
    text-align: center;
    /* background: skyblue; */
    background: url(../images/pic.jpg) no-repeat center; 
    background-size: 100%;
}

input {
    width: 300px;
    height: 30px;
    border: 1px solid rgba(255, 255, 255, 0.5);
    border-radius: 4px;
    margin-bottom: 10px;
}

.user {
    padding-top: 40px;
}

.footer input {
    width: 50px;
    height: 34px;
}

/* 当光标放到按钮上时，鼠标指针为一只小手形状 */
input[type=submit] {
    cursor: pointer;
}
/* 当该input元素获得焦点时，设置背景颜色及盒阴影 */
input:focus {
    background-color: rgba(0, 0, 0, 0.2);
    overflow: hidden;
}
.btn {border-radius: 4px;border-radius: 6px}
/* 当鼠标悬浮在该元素时，设置背景颜色 */
.btn:hover {
    background: rgba(0, 0, 0, 0.2);
}